Premium Content: Display subscriber view to logged in users who have subscribed

[mmtr]

Changes proposed in this Pull Request

• Fix the token subscription service of the Premium Content block so the subscriber view is rendered for logged in users who are subscribed to the plan used in the block, even if the token/auth cookie is missing.
• The block has been completely broken since changes from Remove deprecated blockType.context support WordPress/gutenberg#24155 and Recurring Payments: Replace submit button jetpack#15915 landed in WP.com. The first dropped support for the context property when registering a block in favor of a new usesContext, while the latter dropped support for the submitButtonText attribute of the jetpack/recurring-payments block in favor of the inner jetpack/button block's text attribute. This PR updates the code so block is usable again:

Before	After

Testing instructions

• Modify your /etc/hosts file and point the addresses below to your WP.com sandbox IP:
  • public-api.wordpress.com.
  • subscribe.wordpress.com.
  • The address of a WP.com simple site under a paid plan.
• Add the code below to the /wp-content/mu-plugins/0-sandbox.php file of your WP.com sandbox:

define( 'USE_STORE_SANDBOX', true );
define( 'USE_BILLING_SANDBOX', true );
define( 'BILLINGDADDY_SANDBOX', rtrim( 'https://' . `hostname` ) );

• Checkout this branch and run cd apps/editing-toolkit && yarn dev --sync
• Go to https://wordpress.com/block-editor.
• Select the WP.com simple site you sandboxed above.
• Insert a Premium Content block.
• Make sure you can easily change the plan from the block toolbar.
• Publish the post.
• Visit the post in an incognito/private session.
• Subscribe to the Premium Content plan using a secondary account which don't have access to the WP.com simple site you sandboxed above.
• Make sure the protected content is visible.
• Close the incognito/private session and visit wordpress.com/login in an incognito/private session (this is to make sure any auth cookie is gone).
• Log in as the secondary account you used above.
• Visit the post that contains the Premium Content block.
• Make sure the protected content is visible.

Fixes #45663
Fixes #45498

[matticbot]

Test live: https://calypso.live/?branch=fix/premium-content-login-button-visibility

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[matticbot]

Caution: This PR affects files in the Editing Toolkit Plugin on WordPress.com
Please ensure your changes work on WordPress.com before merging.

D49931-code has been created so you can easily test it on your sandbox. See this FieldGuide page about developing the Editing Toolkit Plugin for more info: PCYsg-ly5-p2

[kwight]

Fantastic, well done @mmtr – and thanks for identifying where the regressions happened ❤️

[kwight]

Tried with multiple users in different logged-in/out states, all behaved as expected. 🎉

[blackjackkent]

Verified on my end as well! Looks good.